As described in “Fundamental Factors Affecting Upper-Room Ultraviolet Germicidal Irradiation—Part I. Experimental,” Journal of Occupational and Environmental Hygiene, 4:5, 321-331,” (2007), the entire contents of which are hereby incorporated by reference, upper-room UVC may greatly lower the concentration of airborne organisms in the lower zone (e.g., below the irradiation field) of the room and thereby control the spread of airborne infection among occupants. Some of the factors determining the suitability of an air sterilization apparatus in clearing the lower air zone of infectious organisms are the quantity of UVC irradiance in the upper air zone, the rate of air mixing between the upper and lower air zones, the specific susceptibility of any particular microbe to UVC, and the control of eye exposure to UVC. See also “Fundamental Factors Affecting Upper-Room Ultraviolet Germicidal Irradiation—Part II. Predicting Effectiveness,” Journal of Occupational and Environmental Hygiene, 4: 352-362,” (2007), the entire contents of which are hereby incorporated by reference.
To maintain these factors in balance, air sterilization systems using UVC irradiation must be carefully chosen to integrate luminaire selection, luminaire placement, and ventilation systems (e.g., air mixing). As can be seen in Table I of “Fundamental Factors Affecting Upper-Room Ultraviolet Germicidal Irradiation,” many attempts have been made to balance these determinants. However, the currently-available air sterilization systems resulting from these attempts fall short, as they are inefficient in their production of UVC irradiation, ineffective in their exposure of room air to UVC, and/or overly expensive. For example, some existing devices are so shielded to avoid room occupant contact with UVC that their efficiency in exposing room air to UVC irradiation is excessively compromised.
Thus, a need exists to provide a more cost-effective, aesthetically pleasing, and improved air sterilization apparatus which can more effectively clear the lower air zone of infectious organisms, achieve the desired rate of air mixing, provide more effective and/or efficient exposure of room air to UVC and which avoids exposure of occupants of the room to UVC.